An apparatus of the type described above must be capable of presenting a newly prepared warp thread exchange system to the loom with the proper orientation so that the exchange can be performed in a minimum of time. A cartridge type exchange would be ideal. The warp thread drawing-in machine which prepares a new warp thread exchange system includes a warp drawing-in carriage that must necessarily be adapted to the requirements of the warp thread drawing-in machine. Similarly, a warp beam lifting carriage that lifts a new warp beam into a loom is primarily adapted for cooperation with the loom. As a result, the warp drawing-in carriage is not necessarily adapted for direct cooperation with a loom nor with the warp beam lifting carriage that lifts the warp beam into the loom and vice versa. The direct cooperation between the warp thread drawing-in carriage and the warp beam lifting carriage poses problems in that these two carriages must be made compatible with each other which heretofore has resulted in expensive equipment that still does not permit an economic storing of prepared warp thread exchange systems between their preparation and their insertion into a loom. Providing a plurality of expensive warp beam lifting carriages for each loom for the purpose of temporarily storing a prepared warp exchange system is economically not feasible.
Incidentally, the warp thread exchange system, also referred to as the warp exchange system, comprises the following components: a warp beam, a warp stop motion unit, a transport unit for the warp stop motion unit, a heald frame, a reed, and warp thread guides. However, conventionally such systems once prepared cannot be stored economically.
U.S. Pat. No. 4,934,413 (Yao), issued Jun. 19, 1990, discloses a method and machine for inserting a warp thread exchange system into a loom. The method of the just mentioned U.S. Patent is performed as follows. First, a new warp exchange system is prepared by drawing-in warp threads into the heald frame of the warp thread exchange system which includes the above mentioned components. Next, the warp beam is inserted into the loom. During the insertion, the tension of the warp threads is sensed to provide a warp tension signal. This warp tension signal is used during the insertion to determine a deviation of the warp thread tension from a given standard warp tension value and the deviation is eliminated by rotating the warp beam so as to keep a difference between the sensed signal and the standard value substantially zero to maintain the proper tension on the warp threads.
The apparatus of U.S. Pat. No. 4,934,413 (Yao) includes a warp beam lifting carriage which also holds the above mentioned warp exchange system into which the warp threads coming from the warp beam have been drawn. The warp beam lifting carriage transfers the warp thread exchange system into the loom. The warp beam lifting carriage includes a device for taking up and lifting the warp beam and further devices, such as vertically and horizontally operable piston cylinder devices, for picking-up the warp exchange system from the drawing-in carriage outside the loom and for delivering the picked up exchange system into a predetermined position relative to the loom. The apparatus of U.S. Pat. No. 4,934,413 (Yao) further includes a sensor that contacts a warp thread guide roller for sensing or picking up the warp thread tension during the insertion of the warp exchange system into the loom. Further, a warp beam rotating device responsive to the above mentioned sensor is provided for rotating the warp beam in response to the signal received from the sensor to maintain a predetermined warp thread tension.
U.S. Pat. No. 4,934,413 (Yao) does not provide any suggestion with regard to the intermediate storage or holding of a prepared warp exchange system in such a way that the system may later be inserted into the loom with a proper orientation relative to the requirements of the loom. However, such proper orientation is necessary for a further reduction in the retooling time required for a warp beam and loom harness exchange. Such retooling in the shortest possible time is very important to the efficient operation of textile mills. Yao also does not provide any disclosure, nor any suggestion with regard to the preparation and storage of the warp exchange system as a cassette type system, whereby the cassette of the prepared warp exchange system is maintained in such a position that it has a proper orientation for the insertion into the loom so that insertion can be accomplished in the shortest possible time, while the storage of the prepared system is completely independent from the actual insertion into the loom.
U.S. Pat. No. 5,197,521 (Graser et al.), issued on Mar. 30, 1993 discloses a warp beam lifting carriage. German Patent Publication DE 4,109,408 (Hiemer), published on Sep. 24, 1992, discloses a weft thread monitoring unit constructed for easy transport.